German Published Patent Application No. 196 50 865 relates to a solenoid valve whose armature has a plurality of parts. The armature includes an armature plate and an armature pin, which is guided in a sliding block. To prevent post-oscillations of the armature plate following the closing of the solenoid valve, a damping device is formed at the magneto armature. Such a device makes it possible to precisely observe, and reproduce, the required short switching times of the solenoid valve. This solenoid valve is intended for use in injection systems, especially in high-pressure injection systems, such as those having a high-pressure common rail.
The damping device by which post-oscillations of the first armature part during its dynamic displacement are able to be damped includes a first armature part, which has a projection facing in the axial direction which, upon displacement of the first armature part, is able to dip into a stationary recess of the sliding block whose design complements that of the projection. The recess with the projection includes a damping chamber which, via a leakage gap, is in connection with a relief chamber surrounding it.
Alternatively, an annular shoulder which is enclosed by a section of the first armature piece may be situated at the armature pin, and an annular shoulder may likewise be located at the first armature piece. Between the annular shoulder of the armature pin and the annular shoulder of the first armature piece a damping chamber is permanently enclosed, which, in turn, is connected via a leakage gap to a relief chamber surrounding it.
According to this design approach, which utilizes a two-part armature able to be actuated by an electromagnet, a stop ring is inserted between the armature pin and the armature plate. The stop ring is designed in the form of an open retaining disk and has a tendency to wear. Considerable signs of wear may occur, which, on the one hand, may lead to play developing between the armature pin and the armature plate and, on the other hand, to the complete destruction of the retaining disk. Even only play developing between the armature pin and the armature plate adversely influences the volume tolerances in the injection, thereby no longer providing, in particular, a repeat accuracy in injections of the most minuscule quantities implemented in rapid succession.